In an effort to understand the role of the hydrolytic (RNase H) of AMV DNA polymerase activity it was found that this activity could be inhibited to a great extent by cyclic nucleotides while minimum inhibition was observed within the synthetic reaction. 32p-labeled AMV 70s RNA was obtained by limited DNA synthesis in the presence of (alpha-32P)dATP, TTP, dGTP. Omitting dCTP leads to the synthesis of a short stretch of DNA, seven nucleotides long (AATGAAG) tagged to the 3' end of the tRNA-32P. With labeled AMV 70s RNA p27, p19 and p15 as well as lysoenzyme, all showed binding activity utilizing mitocellulose filters. However, when the binding mixtures at low salt were irradiated with UV and then made 0.5M NaC1, lysoenzyme, p27, p19 showed much stronger binding to AMV RNA than host 28s RNA under similar conditions. Phosphorylation of reverse transcriptase with endogenous virus protein kinase followed by polymerase antibody affinity chromatography showed significant 32P radioactivity coeluting with polymerase activity. A new labeled peptide appeared on SDS gels.